These printers use the C4871A cartridge:
Click On a Printer to View it's Cartridges
          HP DesignJet 1050
          HP DesignJet 1050 C
          HP DesignJet 1050 C Plus
          HP DesignJet 1055 C
          HP DesignJet 1055 CM
          HP DesignJet 1055 CM Plus